Wheat Water Use Efficiency Research Articles

半干旱区旱地春小麦全膜覆土穴播对土壤水热效应及产量的影响

以春小麦"陇春27"为试材,研究半干旱区旱地全膜覆土穴播对土壤水热效应及小麦产量的影响。结果表明:与裸地平作(CK)相比,全膜覆土穴播(PM)和全沙覆盖平作(SM)增温效果呈"挂钩型",增温效果在小麦拔节期前最为明显,PM 0-25 cm土壤平均温度较CK提高1.8 ℃,全沙覆盖平作提高1.4 ℃,拔节后PM和SM的增温效果逐渐减弱直至消失,而在成熟期又呈现较弱的增温效果。PM和SM能提高小麦出苗后耗水速度并加大耗水量,其中,小麦拔节到扬花期耗水量增加最多,分别较CK平均增加54.93%和31.54%,且此阶段越是干旱,促进耗水作用越明显,PM促进作用大于SM。PM和SM能显著提高小麦阶段性水分利用效率(<em>WUE</em>_b),其中PM以苗期提高最多,2a平均较CK提高365.17%,SM拔节期提高最多,2年平均较CK提高119.00%。PM和SM在增温、促进耗水作用下使小麦各生育期提前并增加单株干重,产量较CK分别平均增加432.28%和375.82%, 水分利用效率(<em>WUE</em>)分别平均增加351.51%和338.29%,而且越干旱年份增产效应愈加明显。可见,PM和SM在越为干旱的年份促进耗水、增产和提高<em>WUE</em>的作用越显著,PM效果强于SM。;The differences between the timing of natural rainfall and demands of crops for water during seasonal drought is one of the main factors restricting crop production in semi-arid areas.As a new agricultural technology, the use of plastic film as mulch to cover the entire soil surface, combined with bunch planting of wheat with no-tillage has several effects; the plastic captures evaporating water and so suppresses evaporation and maintains soil moisture.This significantly improves rainfall use efficiency, allows the full use of light and heat resources, and significantly increases yield of wheat, flax and other crops.Therefore, the use of plastic film as mulch with bunch planting has been widely applied in dryland agriculture in the middle and eastern parts of Gansu Province, China.However, systematic methods for the use of plastic mulch in wheat production are still lacking; in particular, research is lacking on the effects of plastic film mulching with bunch planting on soil temperature, moisture, water consumption, water use efficiency (<em>WUE</em>), and effects on the various growth stage of wheat and on dry matter accumulation.To understand how this new technology improves crop development and yield and how it affects soil hydrothermal conditions, we designed and implemented a field experiment using three treatments: the use of plastic film as mulch to cover the entire soil surface with bunch planting (PM), the use of sand mulching on the entire field and traditional scattered seed planting (SM) and un-mulched planting and with traditional scattered seed planting (CK).The study was carried out to determine the effects of different mulching methods on soil temperature, moisture and yield of spring wheat (<em>Triticum aestivum </em>L.) in the semi-arid area in drylands in central Gansu.In this experiment, we used Long Spring 27 (<em>Triticum aestivum </em>L.) as the test material to study the effects of different mulching methods on soil temperature, moisture and spring wheat yield in a semi-arid area.The results showed that PM and SM increased soil temperature in the entire growth period for spring wheat; this increase in soil temperature is most obvious before the jointing stage of wheat.PM and SM could result in a 1.8 ℃ and 1.4 ℃ increase in average soil temperatures in the 0-25 cm soil layer, respectively, compared with CK.After the jointing stage, the warming effect of PM and SM gradually weakened or disappeared, although it reappeared in a weaker state as the wheat matured.PM and SM could improve the rate of water consumption and increase water consumption after seedling emergence.Water consumption was largest during the jointing-flowering stage and PM and SM increased water consumption up to 54.93% and 31.54%, respectively, compared with CK.With increased drought intensity the effects of the treatments were more obvious at the jointing-flowering stage.PM and SM could improve biomass water use efficiency of wheat (<em>WUE</em>_b) significantly; the improvement was highest (up to 365.17%) at the seedling stage of PM and at the jointing stage of SM (up to 119.00%), compared with CK.PM and SM treatments resulted in increased soil temperatures and improved soil water consumption; therefore, these treatments extended the growing period for spring wheat and increased the dry matter weight per plant.Also PM and SM increased yield by 432.28% and 375.82% and increased <em>WUE</em> by 351.51% and 338.29%, respectively, compared with CK; with increased drought intensity, yield increased more obviously with the PM and SM treatments.Therefore, PM and SM can significantly promote water consumption, increase yield and improve <em>WUE</em> by a higher percentage in a drought year, although the effect is stronger with PM than with SM.

Nitrogen and water use efficiencies of wheat and barley under a Mediterranean environment in Catalonia

In Southern Mediterranean regions, farmers usually grow barley monocultures in drought-prone areas while wheat is grown in better-watered regions. This is based on an assumption of better performance of barley than wheat in terms of productivity and resource capture. Information about the comparative performance of these species under scarce resource availability is rudimentary.The aim of the present work was to compare the performance of bread and durum wheat and barley in terms of water use, nitrogen uptake, water use efficiency and nitrogen use efficiency under Mediterranean environments. Four experiments were conducted on farmers’ fields at Agramunt, in the province of Lleida (Catalonia, north-eastern Spain) during 2004/05, 2005/06 and 2006/07. Treatments consisted of barley, bread wheat and durum wheat grown under different combinations of water (rainfed or irrigated) and nitrogen availabilities.Water and nitrogen availabilities resulted in a wide range of water use efficiency (from 6.3 to 23kggrainha−1mm−1) and nitrogen use efficiency (from 2.9 to 31.8kggrainkgavailableN−1 in soil). Nitrogen uptake was closely and positively related to grain yield and total biomass at maturity for the three species. Nitrogen fertilization modified yield of the three species, mainly through changes in water use efficiency (R2=0.75).Differences between the species were low but existed in relative terms; they were not always in favor of barley. In fact, barley did not consistently outperform bread or durum wheat in terms of resource use or resource use efficiency under poor-yielding conditions. The relative differences between wheat and barley in terms of grain yield (analyzed as wheat yield/barley yield) were explained by the relative differences between them in terms of nitrogen use efficiency and water use efficiency (analyzed as wheat resource use efficiency/barley resource use efficiency).

Effects of Soil Tillage Practice on Dry Matter Production and Water Use Effi-ciency in Wheat

Effects of Soil Tillage Practice on Dry Matter Production and Water Use Effi-ciency in Wheat

Contribution of summer rainfall and nitrogen to the yield and water use efficiency of wheat in Mediterranean-type environments of South Australia

In a worldwide context of agricultural intensification, cropping systems in Mediterranean-type environments have been reducing the frequency of long-fallow in a shift to continuous cropping. The focus of this paper is the short summer fallow between successive winter grain crops in environments of South Australia with winter-dominant rainfall. Our aims were to (i) estimate wheat yield response to summer rainfall, (ii) explain yield responses in terms of capture and efficiency in the use of radiation and water, (iii) explore the incidence of the amount and disposition of stubble on storage of summer rainfall, and (iv) assess the interaction between summer rainfall and nitrogen supply. We used trickle irrigation to manipulate summer water supply in two factorial experiments combining water and stubble treatments, and three factorials combining water and nitrogen supply. Addition of 50–100 mm of water increased soil water content at sowing between 8 and 46 mm compared to controls that only received the background summer rainfall (10–74 mm). Yield gain from additional water input in summer declined from 1.1 t ha −1 to zero when the yield of controls increased from 2.0 to 7.8 t ha −1. Where yield response was related to a single resource, water or nitrogen, capture of radiation and water were major drivers of growth and yield response. Where yield response was related to the interaction between water and nitrogen, both capture and efficiency in the use of resources were important. Amount (0–5 t ha −1) and disposition of stubble (standing or flat) did not affect the amount or distribution of water in soils, and had no effect on grain yield. High nitrogen rate was critical to capture the benefits of additional summer water and reciprocally high water supply was required to capture the benefits of nitrogen fertilisation; this highlights the resource co-limitation for wheat production in these environments. In a water × nitrogen factorial, crops with either low nitrogen or no additional summer water supply had radiation use efficiency ∼1.6 g MJ −1, biomass per unit evapotranspiration ∼33 kg ha −1 mm −1 and yield per unit evapotranspiration ∼15 kg ha −1 which increased to 1.9 g MJ −1, 40 kg ha −1 mm −1 and 18 kg ha −1 mm −1 in crops with both additional water and high nitrogen. Across experiments and treatments, grain number accounted for 88% of the variation in yield. Grain number was proportional to crop growth rate between stem elongation and anthesis; crops with high nitrogen produced 116 ± 5.0 grains per unit crop growth rate and their low nitrogen counterparts 99 ± 4.6. Building evidence from Mediterranean environments worldwide highlights the importance of grain number as the main source of variation in yield and therefore the critical period between stem elongation and anthesis where both water and nitrogen supply are critical.

Winter Wheat Water Use Efficiency in Different Scales

That there existed time and spatial variation for winter wheat water use efficiency (WUE) in different scales in irrigation area could be concluded by studying winter wheat WUE in small scale, middle scale and large scale in irrigation area in 2004~2006 in this paper. It indicated that winter wheat WUE were much more different in the small, the middle and the large scales in different years, which were 1.61kg/m3, 1.30kg/m3 and 0.88kg/m3, respectively. With up scaling, winter wheat WUE was declining in 2004, while increased firstly and then declined in 2005 ~2006.

Effects of Soil Tillage Practice on Dry Matter Production and Water Use Efficiency in Wheat

The objective of this study was to understand the effects of tillage practice on water consumption characteristics and dry matter accumulation and distribution in wheat (Triticum aestivum L.) plant under high-yielding and flexible irrigation conditions. In a fixed position experiment across 3 growing seasons from October 2007 to June 2010, only one wheat cultivar, Jimai 22, was planted in the field. In the 2007–2008 wheat season, 5 tillage treatments were designed, which were strip rotary tillage (SR), strip rotary tillage after subsoiling (SRS), rotary tillage (R), rotary tillage after subsoiling (RS), and plowing tillage (P). The same treatments were arranged in the same field plots in the 2008–2009 and 2009–2010 wheat seasons, except that SRS and RS had no subsoiling. All tillage treatments were irrigated at sowing, jointing, and anthesis stages to designed soil water content based on testing soil moisture before watering. The total water consumption was higher in SRS and RS treatments than in SR and R treatments. Treatment SRS increased the amount of soil water consumption in 0–200 cm soil layers but decreased the soil evaporation, compared to other treatments. Treatments SRS and RS gained the highest amount of dry matter accumulation, grain dry matter partitioning at maturity, and contribution to grain of dry matter assimilation after anthesis, followed by treatment P, and treatments R and SR showed the lowest levels in the above parameters, particularly SR. In the experiment across 3 years, SRS obtained the grain yields of 9409.01 kg ha−1 in 2008, 9613.86 kg ha−1 in 2009, and 9698.42 kg ha−1 in 2010, which were equivalent to that of RS but significantly higher than other treatments. Treatments P and R also exhibited higher yield level than SR treatment. In the 2008–2009 and 2009–2010 growing years, the water use efficiencies of SRS treatment were the highest among treatments, which were 21.39 kg ha−1 mm−1 and 22.09 kg ha−1 mm−1, respectively. Treatment RS also had higher water use efficiency than SR, R, and P treatments. Therefore, SRS is recommended as the optimal tillage practice in high-yielding and water-saving production system in the Yellow-Huai-Hai River Valleys Plain.

Effect of skipping irrigation on growth, yield, yield components and water use efficiency of wheat (Triticum aestivum L.) in semi arid Region of Sudan

The study was conducted for two consecutive winter seasons (2008/09-2009/10) at the Demonstrated Farm, Sudan University of Science and Technology, Shambat, Sudan to study the effect of skipping one irrigation during different developmental stages on growth, yield, yield components and water use efficiency of wheat (Triticum aestivum L.). Condor cultivar was grown under six irrigation treatments at developmental growth stage, in which one-irrigation was skipped at some of growth stages (seedling W1, tillering W2, booting W3, dough W4 and repining stage W5) and irrigation without skipping with intervals of 10 days as control WS. The experimental design was randomized complete block design with four replications. The parameters studied were: plant height, dry matter accumulation, plant/m 2 , tiller/plant, number of spike/m 2 , spikelet/spike, grain/spike, 1000-grain weight, grain yield, straw yield, biomass, harvest index, water use efficiency. The results showed there were highly significant differences in all tested parameters due to skipping irrigation except plant/m 2 in both seasons, and plant height and dry matter accumulation in 45 days reading (booting stage) in the second seasons. Irrigation every 10 days throughout (control) gave higher values (few different with seedling and repining stages) than the other sensitive stages. Although, the resulted showed highly significant effect on the studied parameters biomass, straw and grain yield, harvest index, water use efficiency and protein content. In general irrigation every 10 days with slightly different at skipping on seedling and repining stages gave the highest protein content, grain and straw yield and field water use efficiency. Skipping irrigation during tillering and booting stage must be avoided.

Effect of Root Redundancy on Grain Yield and Water Use Efficiency of Winter Wheat*

A pot experiment was conducted to clarify the effect of root system size(between returning green stage and heading stage) on grain yield and water use effi ciency(WUE) of winter wheat(Triticum aestivum).The results showed that the root to shoot ratio(R/S) of large root system treatment were significantly bigger than that of small root system treatment at heading stage.At flowering stage,large root system treatment had higher photosynthesis and root respiration rate,but lower accumulation of dry matter after flowering compared with small root system.At maturity,small root system treatment had significantly higher grain yield compared with large root system treatment.In addition,small root system treatment improved WUE of wheat(by 33.91% under well watered conditions and 15.82% under moderate drought stress) compared to large root system treatment(P0.05).Therefore,the current study suggested that drought-resistance breeding to improve the grain yield and WUE,at least for wheat,should not be made by targeted selection of progeny with a large R/S ratio for cultivation in arid and semiarid areas.

Modelling the nitrogen-driven trade-off between nitrogen utilisation efficiency and water use efficiency of wheat in eastern Australia

The nitrogen-driven trade-off between nitrogen utilisation efficiency (yield per unit nitrogen uptake) and water use efficiency (yield per unit evapotranspiration) is widespread and results from well established, multiple effects of nitrogen availability on the water, carbon and nitrogen economy of crops. Here we used a crop model (APSIM) to simulate the yield, evapotranspiration, soil evaporation and nitrogen uptake of wheat, and analysed yield responses to water, nitrogen and climate using a framework analogous to the rate-duration model of determinate growth. The relationship between modelled grain yield ( Y) and evapotranspiration (ET) was fitted to a linear-plateau function to derive three parameters: maximum yield ( Y max), the ET break-point when yield reaches its maximum (ET #), and the rate of yield response in the linear phase (Δ Y/ΔET). Against this framework, we tested the hypothesis that nitrogen deficit reduces maximum yield by reducing both the rate (Δ Y/ΔET) and the range of yield response to evapotranspiration, i.e. ET # − E s, where E s is modelled median soil evaporation. Modelled data reproduced the nitrogen-driven trade-off between nitrogen utilisation efficiency and water use efficiency in a transect from Horsham (36°S) to Emerald (23°S) in eastern Australia. Increasing nitrogen supply from 50 to 250 kg N ha −1 reduced yield per unit nitrogen uptake from 29 to 12 kg grain kg −1 N and increased yield per unit evapotranspiration from 6 to 15 kg grain ha −1 mm −1 at Emerald. The same increment in nitrogen supply reduced yield per unit nitrogen uptake from 30 to 25 kg grain kg −1 N and increased yield per unit evapotranspiration from 6 to 25 kg grain ha −1 mm −1 at Horsham. Maximum yield ranged from 0.9 to 6.4 t ha −1. Consistent with our working hypothesis, reductions in maximum yield with nitrogen deficit were associated with both reduction in the rate of yield response to ET and compression of the range of yield response to ET. Against the notion of managing crops to maximise water use efficiency in low rainfall environments, we emphasise the trade-off between water use efficiency and nitrogen utilisation efficiency, particularly under conditions of high nitrogen-to-grain price ratio. The rate-range framework to characterise the relationship between yield and evapotranspiration is useful to capture this trade-off as the parameters were responsive to both nitrogen supply and climatic factors.

Measurement and simulation of diurnal variations in water use efficiency and radiation use efficiency in an irrigated wheat-maize field in the North China Plain

Quantifying diurnal patterns of water use efficiency (WUE) and radiation use efficiency (RUE) for wheat and maize is important for assessing water use by plants and crop productivity. Water and carbon dioxide fluxes from an irrigated wheat-maize double-crop field from November 2002 to October 2003 were measured using the Eddy Covariance method. Evident differences were observed between the diurnal patterns of WUE for wheat and maize. The WUE values of wheat peaked near 9, 15 and 12 mg CO2 g H2O in the morning, and then decreased linearly with time and recovered in the late afternoon (4:00pm) before sunset in March, April and May, respectively. The WUE of maize increased after sunrise and retained stable values of 6, 14 and 12 mg CO2 g H2O from mid-morning to mid-afternoon (10:00am –2:00pm) and then decreased slowly with time until sunset in July, August and September, respectively. Similar patterns were observed in the RUE of wheat and maize. Over the three months of the study, averaged RUE was 1.76 g C MJ−1 for the wheat crop and 1.87 g C MJ−1 for the maize crop. A coupled photosynthesis and transpiration model was used to simulate the diurnal variations in WUE under variable climate conditions. Measurement results and sensitivity analysis show that the difference in the diurnal variation pattern in WUE between wheat and maize resulted from the different carbon fixing mechanisms of wheat and maize.

Yield and water use efficiency of wheat and cotton under alternate furrow and check-basin irrigation with canal and tube well water in Punjab, India

A 4-year field experiment was conducted in a semi-arid area to evaluate the response of each furrow and alternate furrow irrigation in wheat-cotton system using irrigation waters of different qualities in a calcareous soil. Irrigation was applied to each and alternate furrow of bed-planted wheat followed by ridge-planted cotton for comparison with standard check-basin method of irrigation to both the crops. These methods of irrigation were evaluated under three water qualities namely good quality canal water (CW), poor quality tube well water (TW) and pre-sowing irrigation to each crop with CW and all subsequent irrigations with TW (CWpsi + TW). The pooled results over 4 years revealed that wheat grain yield was not affected significantly with quality of irrigation water, but significant yield reduction was observed in alternate bed irrigation under canal water and tube well water irrigations. In cotton, poor quality tube well water significantly reduced the seed cotton yield in all the three methods of planting. The pre-sowing irrigation with canal water and all subsequent irrigations with tube well water improved the seed cotton yield when compared with tube well water alone. However, this yield increase was significant only in alternate furrow irrigation, and the yield obtained was on a par with yield under alternate furrow in CW. When compared to check-basin irrigation, each furrow and alternate furrow irrigation resulted in a saving of 30 and 49% of irrigation water in bed-planted wheat, whereas the corresponding savings in ridge-planted cotton were 20 and 42%, respectively. Reduced use of irrigation water under alternate furrow, without any significant reduction in yield, resulted in 28.1, 23.9 and 43.2% higher water use efficiency in wheat under CW, TW and CWpsi + TW, respectively. The corresponding increase under cotton was 8.2, 2.1 and 19.5%. The implementation of alternate furrow irrigation improved the water use efficiency without any loss in yield, thus reduced use of irrigation water especially under poor quality irrigation water with pre-sowing irrigation with canal water reduced the deteriorating effects on yield and soil under these calcareous soils.

Influence of row spacing on water use and yield of rain-fed wheat (Triticum aestivum L.) in a no-till system with stubble retention

A 3-year field study was undertaken to investigate the effect of row spacing on vegetative growth, grain yield and water-use efficiency of wheat. All 3 years of the study experienced 21–51% below-average rainfall for the growing season. Widening row spacing led to reduced biomass and tillers on per plant basis which could be related to the reduction in light interception by the wheat canopy in the wide rows which in turn could have reduced assimilate production. Reduction in vegetative growth in 54-cm rows translated into a significant reduction in grain yield which was strongly associated (r2 = 0.71) with the loss of spike density. The pattern of crop water use (evapotranspiration, ET) during the growing season was very similar for the three row-spacing treatments. However, there was some evidence for slightly lower ET (~5%) in 54-cm rows in two growing seasons. More importantly, there was no evidence for increased ET during the post-anthesis phase in wide rows as has been speculated by some researchers. Over the 3 years of the study, grain yield declined by 5–8% as row spacing increased from 18 to 36 cm and by a further 12–20% as row spacing increased from 36 to 54 cm. There was a consistent decline in water-use efficiency for grain (WUEG) with increasing row spacing over the 3 years. WUEG declined by 6–11% as crop spacing increased from 18 to 36 cm and declined further by 12–15% as row spacing increased to 54 cm. Lower light interception at wider row spacing could have reduced assimilate production by wheat as well as increased soil evaporation due to lower shading of the soil surface in more open canopies. Growers adopting wider row spacing on these relatively heavy textured soils are likely to experience some reduction in grain yield and WUEG. However, some growers may be prepared to accept a small yield penalty from intermediate row spacing as a trade-off for increased stubble retention and soil health.

Quantification of wheat water-use efficiency at the shire-level in Australia

In eastern Australia, latitudinal gradients in vapour pressure deficit (VPD), mean temperature (T), photosynthetically active radiation (PAR), and fraction of diffuse radiation (FDR) around the critical stage for yield formation affect wheat yield and crop water-use efficiency (WUE = yield per unit evapotranspiration). In this paper we combine our current understanding of these climate factors aggregated in a normalised phototermal coefficient, NPq = (PAR· FDR)/(T · VPD), with a shire-level dynamic model of crop yield and water use to quantify WUE of wheat in 245 shires across Australia. Three measures of WUE were compared: WUE, the ratio of measured yield and modelled evapotranspiration; WUEVPD, i.e. WUE corrected by VPD; and WUENPq, i.e. WUE corrected by NPq. Our aim is to test the hypothesis that WUENPq suits regional comparisons better than WUE or WUEVPD. Actual median yield at the shire level (1975–2000) varied from 0.5 to 2.8 t/ha and the coefficient of variation ranged from 18 to 92%. Modelled median evapotranspiration varied from 106 to 620 mm and it accounted for 42% of the variation in yield among regions. The relationship was non-linear, and yield stabilised at ~2 t/ha for evapotranspiration above 343 mm. There were no associations between WUE and rainfall. The associations were weak (R2 = 0.09) but in the expected direction for WUEVPD, i.e. inverse with seasonal rainfall and direct with off-season rainfall, and strongest for WUENPq (R2 = 0.40).We suggest that the effects of VPD, PAR, FDR, and T, can be integrated to improve the regional quantification of WUE defined in terms of grain yield and seasonal water use.

Influence of planting pattern with rainwater harvesting and row spacing on yield and water use efficiency of wheat

In order to increase the use efficiency of natural precipitation resource,the effects of planting pattern with rainwater harvesting and row spacing on wheat yield and water use efficiency were analyzed in a random block design experiment in Linfen,Shanxi Province.The results show that average wheat yield of the planting patterns with 1:1.5 and 1:1 proportion of rainfall collection area to planted field area is significantly higher than that of open field cultivation (CK).When row spacings of 1:1.5 and 1 1 planting patterns,and open field cultivation are 11.3 cm,15 cm and 15 cm respectively,yield increase is more significant.Plant height,per-plant tiller number and per-plant green leaf number at the jointing stage under planting patterns of 1:1.5 and 1:1 are higher than that under open field cultivation.Water use efficiency in 1:1.5,1:1 planting patterns and open field cultivation is 19.8 kg·mm-1·hm-2,17.4 kg·mm-1·hm-2 and 14.3 kg·mm-1·hm-2 respectively.Dynamics of soil water for different planting patterns with rainwater harvesting at each growth stage are synchronously determined.

Response of wheat to subsoil salinity and temporary water stress at different stages of the reproductive phase

To examine the effects of subsoil NaCl salinity in relation to water stress imposed at different growth stages, wheat was grown in a heavy texture clay soil (vertosol) under glasshouse conditions in polythene lined cylindrical PVC pots (100 cm long with 10.5 cm diameter) with very low salinity level (ECe 1.0 dS/m; ESP 1.0 and Cl 30 mg/kg soil) in top 10 cm soil (10–20 cm pot zone) and low salinity level (ECe 2.5 dS/m, ESP 5, and Cl 100 mg/kg soil) in top 10–20 cm soil (20–30 cm pot zone). The plants were exposed to three subsoil salinity levels in the 20–90 cm subsoil (30–100 cm pot zone) namely low salinity (ECe: 2.5 dS/m, ESP: 5, Cl: 100 mg/kg soil), medium salinity (ECe: 4.0 dS/m, ESP: 10, Cl: 400 mg/kg) and high salinity (ECe: 11.5 dS/m, ESP: 20, Cl: 1950 mg/kg) in the subsoil (20–90 cm soil layer: 30–100 cm pot zone). Watering of plants was withheld for 20 days commencing at either early booting or anthesis or mid grain filling, and then resumed until maturity, and these treatments were compared with no water stress. Water stress commencing at anthesis stage had the most depressing effect on grain yield and water use efficiency of wheat followed by water stress at grain filling stage and early booting stage. High subsoil salinity reduced grain yield by 39.1, 24.3%, and 13.4% respectively in plants water-stressed around anthesis, early booting, and mid grain filling compared with 36.6% in well-watered plants. There was a significant reduction in root biomass, rooting depth, water uptake and water use efficiency of wheat with increasing subsoil salinity irrespective of water regimes. Plants at high subsoil salinity had 64% of their root biomass in the top 0–30 cm soil and there was a marked reduction in subsoil water uptake. Roots also penetrated below the non-saline surface into salinised subsoil and led to attain high concentration of Na and Cl and reduced Ca/Na and K/Na ratio of flag leaf at anthesis stage. Results suggest that high subsoil salinity affects root growth and water uptake, grain yield and water use efficiency even in well water plants. Water stress at anthesis stage had the most depressing effect on wheat.

Effects of Water Deficit and Spraying of Dessicant on Yield, Yield Components and Water Use Efficiency of Wheat Genotypes

To evaluate yield, yield components and water use efficiency of bread wheat in water stress conditions and spraying of dessicant, a field experiment was carried out in 2006-2007 and 2007-2008. Main plots were assigned to two levels of water stress treatments; D1: optimum irrigation and D2: cessation of watering from anthesis to maturity stages. Sub plots were assigned to eight bread wheat genotypes; and assimilates limitations with two levels: P1: no source limitation and P2: inhibition of current photosynthesis were in sub-sub plots. Grain yield, biological yield, harvest index, the number of grains per spike, thousand grain weight and water use efficiency were significantly influenced by irrigation treatments and source limitation. Grain Yield (GY) significantly decreased by 35 and 68% under water deficiency and postanthesis photosynthetic inhibition, respectively; compared with control. Water use efficiency was higher for well-watered compared with postanthesis drought stress conditions. WUEgrain decrease due to water deficit was attributed to grain yield reduction. Under water stress, current photosynthetic inhibition reduced grain yield by 62%, but under well-watered condition; it significantly decreased grain yield by 71%, that indicate the source is limititing factor under different irrigation regimes. Considering that C-81-10, 9103 and 9116 genotypes showed the highest grain yield, potential for reserves and remobilizations of assimilates under different irrigation conditions; thus, these genotypes could be introduced as promising in breeding programs for arid and semi-arid regions.

Effect of irrigation and nitrogen application methods on input use efficiency of wheat under limited water supply in a Vertisol of Central India

Field experiments were conducted in a deep Vertisol at the Indian Institute of Soil Science, Bhopal during the years 2001–2005 to assess the effect of five different irrigation strategies through combinations of sprinkler and flood irrigation and two N application methods on yield and water use efficiency of wheat (cv WH 147). The amount of irrigation applied each year differed according to the availability of water in the water harvesting pond to simulate the actual water crisis faced by the farmers in this region during these years due to monsoon failure. Results indicated that when wheat was grown only with 8-cm irrigation at sowing or 14 cm up to the crown root initiation stage, dry sowing of wheat immediately followed by sprinkler and subsequent irrigation through flooding produced the highest yield and water and nitrogen use efficiencies. However, when 20-cm irrigation was supplied up to the flowering stage or 14-cm irrigation was supplied up to tillering stage through sprinkler in 4 and 3 splits, respectively, at critical growth stages, maximized the grain yield and water and nitrogen use efficiencies. Across the years, the crop yield and water and nitrogen use efficiencies increased with increase in water supply.

Can carbon isotope discrimination and ash content predict grain yield and water use efficiency in wheat?

Abstract Drought is the main factor affecting crop grain yield. Increasing grain yield under drought and crop water use efficiency (WUE) is essential for enhancing world crop production and food availability. The objective of this study, carried out in India on 20 durum wheat cultivars, under three water regimes (full irrigation, limited irrigation and residual soil moisture) and during two seasons, was to investigate the potential use of plant traits (particularly carbon isotope discrimination, Δ, and ash content, ma) to predict grain yield and WUE in wheat. WUE components were estimated using a soil water balance model (Budget) allowing comparison of environments in data scarce situations. A highly significant correlation was noted between grain yield and grain Δ across water regimes. However, the associations between grain yield, Δ and ma were found to depend highly on the water regime and environmental conditions. The association between grain yield and grain Δ was significant under full irrigation in season 1 and under residual soil moisture in season 2. Significant positive correlations were noted in both seasons between grain yield and leaf Δ under residual soil moisture and between grain yield and leaf ash content at anthesis under limited irrigation. A significant correlation was found across environments between grain and leaf Δ and T, the quantity of water transpired during the growth cycle, as estimated by the soil water balance model. T also significantly correlated to grain and leaf ma. Variation in WUE across environments was driven more by runoff, drainage and soil evaporation than by harvest index and transpiration. The associations between WUE and transpiration, runoff and Δ were negative but not significant. WUE was significantly correlated with leaf and grain ma at maturity. The study indicates that Δ and ma can be used as indirect selection criteria for grain yield and suggests that ma is a good predictor of transpiration, grain yield and WUE across environments. The use of mechanistic models that allows differentiating between cultivars should permit in a next future to analyze the relationships between WUE, Δ and ma across cultivars and evaluate the possibility to use these traits as predictors of WUE in wheat breeding programs.

Responses of crop yield and water use efficiency to climate change in the North China Plain

Based on future climate change projections offered by IPCC, the responses of yields and water use efficiencies of wheat and maize to climate change scenarios are explored over the North China Plain. The climate change projections of 21st century under A2A, B2A and A1B are from HadCM3 global climate model. A climate generator (CLIGEN) is applied to generate daily weather data of selected stations and then the data is used to drive CERES-Wheat and Maize models. The impacts of increased temperature and CO 2 on wheat and maize yields are inconsistent. Under the same scenario, wheat yield ascended due to climatic warming, but the maize yield descended. As a more probable scenario, climate change under B2A is moderate relative to A2A and A1B. Under B2A in 2090s, average wheat yield and maize yield will respectively increase 9.8% and 3.2% without CO 2 fertilization in this region. High temperature not only affects crop yields, but also has positive effect on water use efficiencies, mainly ascribing to the evapotranspiration intensification. There is a positive effect of CO 2 enrichment on yield and water use efficiency. If atmospheric CO 2 concentration reaches nearly 600 ppm, wheat and maize yields will increase 38% and 12% and water use efficiencies will improve 40% and 25% respectively, in comparison to those without CO 2 fertilization. However, the uncertainty of crop yield is considerable under future climate change scenarios and whether the CO 2 fertilization may be realized is still needed further research.

Effect of water stress on carbon isotope discrimination and Rubisco activity in bread and durum wheat genotypes.

Carbon isotope discrimination (CID) has been suggested as an indirect tool for selection of water use efficiency in wheat. This study evaluates the role of Rubisco activity in regulating carbon isotope discrimination (CID) and discriminate the response of durum (PDW-233) and bread (C-306, HD-2329) wheat genotypes for carbon isotope discrimination and Rubisco activity under induced water stress hydroponically created by using different concentrations of PEG. In C-306, a well known drought tolerant genotype, CID was positively correlated with Rubisco activity. In C-306 CID was positively correlated with both Rubisco activity (r = 0.588* at 5). A positive but not a strong correlation was observed between Rubisco activity and CID (r = 0.418) in durum type PDW-233. Although in HD-2329 the Rubisco activity (r = 0.303) was positively correlated with CID, the correlations were not significant. We show that carbon isotope discrimination technique is a potential tool for selection of lines with high Rubisco activity in the wheat breeding program.